Field of the Invention
This invention relates in general to cathode sputtering techniques in particular to a new and useful sliding layer produced by cathode sputtering.
The invention relates to a laminate material having at least one layer for sliding a "sliding layer", hereinafter referred to as an "overlay", which overlay is applied by cathode sputtering, wherewith said overlay is comprised of a mixture of particles sputtered-on in a statistical distribution [i.e., of the particle diameters], each of which particles is comprised of a metallic material which forms a solidly coherent matrix and at least one other metallic material which other metallic material when in the solid state is practically insoluble in or undetachable from the material of said matrix. The invention further relates to a method of manufacturing the inventive laminate, and to a practical application of same i.e., use of the laminate.
Sliding layers as surface layers of laminate materials are used, e.g., for bearing seats of internal combustion engines. Such layers must have the following properties, among others: lower hardness than the material of the shaft, high resistance to dynamic stresses of an alternating nature, high shear strength, thermal stability of mechanical properties, and high corrosion resistance. These requirements are met by mixtures of lead or tin with other metals which lend mechanical strength by forming a coherent matrix, and which other metals are themselves corrosion resistant and do not dissolve tin or lead (e.g., Al, Cr, or Ni). Laminates with lead-containing or tin-containing overlays, and methods of manufacturing same by cathode sputtering, are described in Ger. Pats. 2,853,724 and 2,914,618, and in Ger. OS 34 04 880. When these methods have been used, substantial problems have arisen with regard to achieving high adhesive strength and bonding strength between the substrate and the applied overlay. Furthermore, these methods lead to a relatively coarse structure of the overlay, with randomly distributed inclusion particles of Sn or Pb of several micron diameter. Such a structure of the overlay leads to corresponding degradation of the corrosion resistance properties.
In addition, according to the state of the art it is considered important for an overlay applied by sputtering and based on an alloy composition AlSn20 in a conventional steel/Cu/Pb three-layer laminate arrangement to have at least a finer distribution of the Sn-containing particles than the rolled layers produced by ordinary methods. Nonetheless, even such overlays lead to poorly defined, heterogeneous mixtures of Al and Sn. Precise data on mean particle size in such overlays, and on reproducible reaction conditions (i.e., reaction conditions for producing reproducible product quality) for manufacturing such overlays have not been made public thus far (see Engle, U., 1986, "Development and testing of new multilayer materials for modern engine bearings: Part 2--copper-lead three-layer bearings with sputtered overlay", in SAE Tech.Pap. Ser., Int. Cong. and Expo., Detroit, Feb. 24-28, pp. 76-77).
According to the state of the art it has been proposed to harden the matrix by appropriate incorporation of oxides ("dispersion hardening"). In practice this has also led to major problems. Thus, for a matrix comprised of Al, oxide particles in amounts of 0.1-0.5 wt.% have been prescribed (Ger. Pat. 2,914,618 Col. 5). Such concentrations are very difficult or impossible to control in manufacturing of, e.g., sliding bearings, on a large serial production scale. The result again is sharp variations in properties of the overlay and unsatisfactory reproducibility of the method of producing the overlays.